The present invention relates to a hatch locking mechanism for the battery compartment of a wristwatch and, more particularly, to a novel and improved hatch locking mechanism which is operable by the pivotal movement of a lever. The movement of the lever to a locking position serves to move and lock a hatch cover for the battery compartment into sealing engagement with the watch case.
Heretofore, the changing of a wristwatch battery has required the removal of the rear cap of the watchcase and the battery changing operation has normally been left to a watchmaker, since the operation is too difficult to be performed by the user. However, it is desirable that the user be able to replace batteries and, in fact, there has already been proposed a wristwatch provided with a battery compartment formed at the rear side of the watchcase and including a hatch mechanism which enables this portion to be removed.
In a known hatch-type mechanism, the mouth of the battery compartment includes at its inner periphery an annular groove which receives a ring-shaped seal against which a hatch is screw-clamped. However, these components are relatively small and the operation is characterized by considerable difficulty, especially in positioning the seal at a predetermined location. Furthermore, the relatively higher sealing force normally employed to meet waterproof requirements results in the risk that the hatch may be lifted by the resiliency of the seal unless the hatch is screw-clamped with a sufficient depression exerted upon the hatch. Even when the screw is tightened with the right hand while a depression is exerted with a finger of the left hand upon the hatch, it is difficult to accomplish the desired operation. Even if the screw is properly tightened, a possible deviation of the seal from its predetermined position will reduce the water-proof effect. Formation of a thread around the hatch itself could somewhat facilitate the locking operation, but this necessarily increases the thickness of the hatch itself, often to an undesirable extent, since the modern wristwatch generally tends to have its thickness reduced more and more. With this measure, furthermore, the hatch configuration is limited to the circular one. Accordingly, this measure is not practical, since it is not applicable to the oval or square hatch, depending on the type of wristwatch.
A mechanism of the so-called "snap type," in which the hatch made of elastic material is also employed, and a mechanism in which the hatch can be locked with only a slight rotation thereof under a depression being exerted upon the hatch are also well known. In both cases, the operation of hatch locking is extremely difficult, since the hatch must be clamped while depressing the hatch with the finger after the seal has been positioned. In addition, a relatively high degree of precision is usually required in making the groove of the rear cap which is adapted to receive the seal, since the desired waterproof effect will be reduced unless the seal is brought into close contact with the groove.